linux-kernel - Re: [RFC PATCH 2/2] tracing: add testable specifications for event_enable

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Message-ID: <CA+wEVJbjhLmA4ZR5w7s6QDCfjET=Pf2J9PsFhC2wdO1nQ5YY+A@mail.gmail.com>
Date: Wed, 2 Jul 2025 18:12:11 +0200
From: Gabriele Paoloni <gpaoloni@...hat.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: mhiramat@...nel.org, mathieu.desnoyers@...icios.com, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	acarmina@...hat.com, chuck.wolber@...ing.com
Subject: Re: [RFC PATCH 2/2] tracing: add testable specifications for event_enable_write/read

On Wed, Jul 2, 2025 at 5:12 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Wed, 2 Jul 2025 16:59:29 +0200
> Gabriele Paoloni <gpaoloni@...hat.com> wrote:
>
> > Mmm got it. What about
> >
> > * Function's expectations:
> > * - This function shall lock the global event_mutex before performing any
> > *   operation on the target event file and unlock it after all operations on
> > *   the target event file have completed;
>
> Since 99% of the time that a lock is taken in a function it is
> released, I think that should be the default assumption here, and only
> when a lock is taken and not release, that should be explicitly called
> out.
>
> And also we should remove "This function" we know that these
> requirements are for this function.
>
>   - The global event_mutex shall be taken before performing any
>     operation on the target event.
>
> Should be good enough.
>
> If the lock can be released and taken again, that too should be
> explicit in the requirements otherwise it is assumed it is taken once
> and not released until the operation is completed.



>
> > *
> > * - This function shall format the string copied to userspace according to
> > *   the status flags retrieved from the target event file:
> > *    - The first character shall be set to "1" if the enabled flag is
> > set AND the
> > *      soft_disabled flag is not set, else it shall be set to "0";
> > *    - The second character is optional and shall be set to "*" if either the
> > *      soft_disabled flag or the soft_mode flag is set;
> > *   - The string shall be terminated by a newline ("\n") and any remaining
> > *      character shall be set to "0";
>
>  - The string copied to user space shall be formatted according to the
>    status flags from the target event file:
>
>    - If the enable flag is set AND the soft_disable flag is not set then
>      the first character shall be set to "1" ELSE it shall be set to "0"
>
>    - If either the soft_disable fag or the soft_mode flag is set then the
>      second character shall be set to "*" ELSE it is skipped.
>
> I think the above is easier to read and is a bit more consolidated.
> Stating the status then the effect is also easier to read.

I will add all your suggestions in v4.
Many thanks for your review!
Gab

>
> -- Steve
>
>
> > *
> > * - This function shall invoke simple_read_from_buffer() to perform the copy
> > *   of the kernel space string to ubuf.
> >
> > (pls note that the check on cnt has been removed in v3 that is out already)
>